User terminal, radio base station, radio communication system, and radio communication method

ABSTRACT

A channel state is adequately reported even if the number of component carriers configurable to a user terminal is expanded to six or more. The user terminal for communicating with a radio base station by use of six or more component carriers includes a measuring section configured to measure reception quality of a downlink channel of each of the component carriers, and a transmission section configured to periodically transmit information relating to the reception quality in accordance with timing specified from the radio base station. The transmission section transmits information relating to reception quality of a plurality of component carriers, at a same subframe, by use of PUSCH or a PUCCH format having a larger capacity as compared with a PUCCH format for existing systems in which a number of configured component carriers is five or less.

TECHNICAL FIELD

The present invention relates to a user terminal, radio base station,radio communication system, and radio communication method, which areapplicable to the next-generation mobile communication system.

BACKGROUND ART

In UMTS (Universal Mobile Telecommunications System) networks, for thepurpose of a higher data rate, smaller delay, and/or the like, Long TermEvolution (LTE) has been specified (Non-Patent Literature 1). Further,for the purpose of a wider band and higher speed than LTE, an LTEsuccessor system called “LTE Advanced” (which is also referred to as“LTE-A”) has been studied and specified as LTE Rel. 10/11.

The system band of LTE Rel. 10/11 includes at least one ComponentCarrier (CC) that is defined in units of the system band of an LTEsystem. Formation of a wider band by combining a plurality of CCs inthis way is called “Carrier Aggregation” (CA). Further, in LTE Rel. 11,there has been introduced Multiple Timing Advances (MTA) that enablestiming control to be performed differently among CCs. By introducingMTA, it becomes possible to realize CA with a plurality of CCs, whichare formed at a plurality of transmission/reception points (for example,a radio base station and an RRH (Remote Radio Head)) arranged atsubstantially different positions.

Further, for LTE Rel. 12, which is an LTE successor system furthersucceeding, studies have been conducted on various scenarios of using aplurality of radio base stations in different frequency bands(carriers). For example, studies have been conducted such that CAutilizing MTA described above is applied in a case where a plurality ofcells are formed of a single radio base station, and that DualConnectivity (DC) is applied in a case where a plurality of cells areformed of radio base stations completely different from each other.

CITATION LIST Non-Patent Literature

[Non-Patent Literature 1] 3GPP TS 36.300 “Evolved Universal TerrestrialRadio Access (E-UTRA) and Evolved Universal Terrestrial Radio AccessNetwork (E-UTRAN); Overall description; Stage 2”

SUMMARY OF INVENTION Technical Problem

In the case of CA for the LTE successor systems (LTE Rel. 10 to 12)described above, the number of CCs settable (configurable) per userterminal (UE: User Equipment) is limited to five at most. For LTE Rel.13, which is an LTE successor system further succeeding, studies havebeen conducted to configure six or more CCs by relaxing the limit of thenumber of CCs settable per user terminal, in order to realize radiocommunication more flexibly and at a higher speed.

However, if the number of CCs settable to a user terminal is expanded tosix or more (for example, 32), it is thought that a transmission methodfor the existing (legacy) systems (Rel. 10 to 12) becomes difficult toapply as it is. For example, in the existing systems, when a channelstate is periodically reported from a user terminal, a so-calledperiodic CQI (P-CQI: Periodic-Channel Quality Indicator) is transmittedon an uplink control channel (PUCCH: Physical Uplink Control CHannel) byuse of a format on the premise of five CCs or less. Accordingly, alsowhere the number of CCs is set to be six or more, it is expected that atransmission technique for realizing an adequate channel state report isrequired.

The present invention was made in view of such a respect, and it is anobject of the invention to provide a user terminal, radio base station,radio communication system, and radio communication method that enable achannel state to be adequately reported even where the number ofcomponent carriers settable to a user terminal is expanded to six ormore.

Solution to Problem

One aspect of a user terminal of the present invention is a userterminal for communicating with a radio base station by use of six ormore component carriers. The user terminal comprises a measuring sectionconfigured to measure reception quality of a downlink channel of each ofthe component carriers, and a transmission section configured toperiodically transmit information relating to the reception quality inaccordance with timing specified from the radio base station. Thetransmission section transmits information relating to reception qualityof a plurality of component carriers, at a same subframe, by use ofPUSCH or a PUCCH format having a larger capacity as compared with aPUCCH format for existing systems in which a number of configuredcomponent carriers is five or less.

Advantageous Effects of Invention

According to the present invention, it is possible to adequately reporta channel state even where the number of component carriers settable toa user terminal is expanded to six or more.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for explaining existing carrier aggregation andcarrier aggregation expanded therefrom;

FIG. 2 is a diagram illustrating a table that prescribes existing P-CQIreporting periods;

FIG. 3 is a diagram for explaining an example of P-CQI transmissionaccording to a first example;

FIG. 4 is a diagram for explaining an example of P-CQI transmissionaccording to a second example;

FIG. 5 is a diagram for explaining an example of P-CQI transmissionaccording to a third example;

FIG. 6 is a diagram for explaining an example of P-CQI transmissionaccording to a fourth example;

FIG. 7 is a diagram for explaining an example of P-CQI transmissionaccording to a fifth example;

FIG. 8 is a schematic configuration diagram of a radio communicationsystem according to an embodiment of the present invention;

FIG. 9 is a diagram illustrating an example of the entire configurationof a radio base station according to the embodiment of the presentinvention;

FIG. 10 is a diagram illustrating an example of a functionalconfiguration of the radio base station according to the embodiment ofthe present invention;

FIG. 11 is a diagram illustrating an example of the entire configurationof a user terminal according to the embodiment of the present invention;and

FIG. 12 is a diagram illustrating an example of a functionalconfiguration of the user terminal according to the embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

FIG. 1 is an explanation diagram of carrier aggregation (CA) in an LTEsuccessor system (LTE Rel. 12), and of CCs of CA being studied in LTERel. 13. As illustrated in FIG. 1, in the case of LTE Rel. 12, at mostfive CCs (CC #1 to CC #5) are set per user terminal, but, in the case ofLTE Rel. 13, expanded carrier aggregation (CA enhancement) for settingsix or more CCs (cells) has been studied. For the expanded CA, asillustrated in FIG. 1, studies have been conducted such that at most 32CCs (CC #1 to CC #32) are configured (set) per user terminal. In thiscase, communication can be performed with respect to a user terminal byuse of a bandwidth of at most 640 MHz. Consequently, for example, it ispossible to increase or change the number of CCs to be used forcommunication, and thereby to realize radio communication flexibly andat a high speed.

Further, for LTEs since Rel. 13, studies have been conducted by alsotargeting an operation in a frequency band that requires no license,i.e., in an unlicensed band. As the unlicensed band, for example, 2.4GHz-band or 5 GHz-band is used as in Wi-Fi. In LTE Rel. 13, a studytarget is carrier aggregation between a licensed band and an unlicensedband (LAA: License-Assisted Access), and studies have been conductedalso on CA combining a licensed band of 100 MHz and an unlicensed bandof 300 MHz, for example.

On the other hand, as described above, in the existing systems, P-CQIsare transmitted on an uplink control channel (PUCCH) by use of a formaton the premise of five CCs or less. Such P-CQIs are calculatedindividually for the respective CCs in the user terminal, and arereported individually for the respective CCs (for example, by use of RRCor the like) to a radio base station, at a period set by the radio basestation. When the P-CQIs are to be transmitted, if there is notransmission data (if there is no PUSCH), the P-CQIs are transmitted inaccordance with PUCCH format 2, and, if there is transmission data (ifthere is PUSCH), the P-CQIs are transmitted by use of PUSCH. However,P-CQIs of a plurality of CCs cannot be transmitted at the same subframe(the same TTI (Transmission Time Interval)) in one uplink CC. Forexample, if P-CQIs of a plurality of CCs overlap with each other at thesame subframe, the user terminal reports only one P-CQI in accordancewith a predetermined rule, and stops (drops) transmission of the otherP-CQIs.

In a case where this P-CQI reporting technique for the existing systemsis applied to the above-described CA that has been studied for LTE Rel.13, only a P-CQI of one CC is reported at one subframe (one TTI).Accordingly, it takes time to report P-CQIs of all the CCs, and thus theP-CQI reporting period corresponding to each of the CCs ends up beingprolonged. For example, in the case of CA using 32 CCs, even if all theuplink subframes are used to transmit the P-CQIs, the shortest periodbecomes 32 ms. In general, the radio base station side is desired totimely acquire the CQIs of the user terminal, and so it is notpreferable to prolong the P-CQI reporting period for each CC.

FIG. 2 illustrates a table example that prescribes P-CQI reportingperiods in an existing system. There are prescribed 2, 5, 10, and 20 forperiods N_(pd), but these periods cannot be adopted in CA with 20 CCs ormore.

The inventors of the present invention paid attention to these featuresof CA, and have arrived at the concept that P-CQIs of a plurality of CCsare transmitted at the same subframe by use of PUSCH or a PUCCH format(which will be referred to as “high capacity PUCCH format”, hereinafter)having a larger capacity as compared with a PUCCH format for theexisting (legacy) systems in which the number of configured CCs is fiveor less.

Next, an embodiment will be described below in detail. In the followingdescription, for the sake of convenience in description, an explanationwill be given of a case where the number of CCs settable per userterminal is 32 in performing CA. However, in a radio communicationsystem according to the embodiment, the number of CCs settable per userterminal is not limited thereto, but may be changed as needed.

First Example

In the first example, when P-CQI reporting is performed, the highcapacity PUCCH format described above is used, and thereby P-CQIscorresponding to a plurality of CCs are transmitted at the same uplinksubframe (the same TTI). In this example, an explanation will be givenof a case where P-CQIs of eight CCs are transmitted at one subframe byuse of the high capacity PUCCH format. However, the number of CCs to betransmitted by use of the high capacity PUCCH format is not limitedthereto.

For each of the CCs, the period and timing for P-CQI reporting can beset in advance. For example, in the example illustrated in FIG. 3, asregards CCs #1 to #8, there is set a period of 20 ms together withtiming for performing transmission at the initial subframe on the uplinkillustrated in FIG. 3 (the first subframe from the left). As regards CCs#9 to #16, there is set a period of 20 ms together with timing forperforming transmission at the second subframe on the uplink illustratedin FIG. 3 (the second subframe from the left). As regards CCs #17 to#24, there is set a period of 10 ms together with timing for performingtransmission at the third subframe on the uplink illustrated in FIG. 3(the third subframe from the left). As regards CCs #25 to #32, there isset a period of 10 ms together with timing for performing transmissionat the fourth subframe on the uplink illustrated in FIG. 3 (the fourthsubframe from the left).

As a result, on the uplink, the first subframe illustrated in FIG. 3 isused to transmit a plurality of P-CQIs corresponding to the CCs #1 to#8, the second subframe is used to transmit a plurality of P-CQIscorresponding to the CCs #9 to #16, the third subframe is used totransmit a plurality of P-CQIs corresponding to the CCs #17 to #24, andthe fourth subframe is used to transmit a plurality of P-CQIscorresponding to the CCs #25 to #32. Further, since the CCs #17 to #24are set with a period of 10 ms, the 13th subframe on the uplink in FIG.3 is also used to transmit their latest P-CQIs. Similarly, for the CCs#25 to #32, the 14th subframe is also used to transmit their latestP-CQIs.

For the control according to the first example, the high capacity PUCCHdescribed above is set (configured) in the user terminal. Further, theperiod and timing for P-CQI reporting for each of the CCs are set(configured) from a radio base station by use of RRC or the like. Theuser terminal transmits P-CQIs of at most eight CCs, at the samesubframe (the same TTI), by use of the high capacity PUCCH format, inaccordance with the above period and timing.

In order to provide a new format (high capacity PUCCH format) applicablein this embodiment, for example, there may be considered a method ofreducing the orthogonal spread block codes of PUCCH format 3. Accordingto existing PUCCH format 3, the same bit sequence is copied to five orfour time symbols, and the orthogonal spread codes are multiplied.Different orthogonal spread codes are multiplied for respective users,so that an orthogonal multiplex state is formed with respect to eachother. For example, by setting the orthogonal code length to be “1”,different information bit sequences can be applied to the five or fourtime symbols. However, in this case, the number of users that can bemultiplexed onto the same PRB is reduced. For example, where theorthogonal code length is “1”, the transmittable bit sequence lengthbecomes five times or four times existing PUCCH format 3, but the numberof users that can be multiplexed becomes one.

As the new format (high capacity PUCCH format), there may be alsoconsidered to define a PUCCH format using frequency resources of twoPRBs or more. For example, if a PUCCH format for performing transmissionby two PRBs is defined based on the configuration of existing PUCCHformat 3, it becomes possible to transmit bit sequences twice as largeas existing PUCCH format 3. As regards which number of PRBs is used andwhich PRB is used for performing transmission: they may be determined bythe UE in accordance with the number of bits of an HARQ-ACK or CSI (CQIor the like) to be multiplexed to PUCCH; they may be specified inadvance by use of higher layer signaling, such as RRC; or they may beindicated by the base station for each subframe by use of a controlsignal, such as PDCCH.

Alternatively, as the high capacity PUCCH format, there may be alsoconsidered to define a PUCCH format using multilevel modulation of 16QAM or more. For example, if a PUCCH format where Uplink ControlInformation (UCI) is modulated using 16 QAM is defined based on theconfiguration of existing PUCCH format 3, it becomes possible totransmit bit sequences twice as large as existing PUCCH format 3. Asregards which modulation scheme is used: this may be determined by theUE in accordance with the number of bits of an HARQ-ACK or CSI to bemultiplexed to PUCCH; this may be specified in advance by use of higherlayer signaling, such as RRC; or this may be indicated by the basestation for each subframe by use of a control signal, such as PDCCH.

In the explanation described above, “based on the configuration ofexisting PUCCH format 3” means to reuse: a coding method to UCI, such asan HARQ-ACK or CSI; an order of mapping to radio resources; the temporalsymbol position of a reference signal contained in PUCCH format 3; andthe like. As a reference signal sequence for generating the referencesignal, it is assumed to use a sequence different from that with onePRB. For example, there may be considered to use a reference signalsequence to be multiplexed to PUSCH with two PRBs defined in theexisting LTE.

Alternatively, PUSCH may be utilized as a new format where uplinkcontrol signals of six or more CCs can be multiplexed. In this case,even when the user terminal does not perform transmission of PUSCH, itperforms transmission of uplink control signals by PUSCH.

In the existing systems, if UL data transmission and UCI transmissionare generated at the same subframe, the user terminal applies a methodof multiplexing the UCI in PUSCH indicated to perform the UL datatransmission (Piggyback). Unlike PUCCH, PUSCH does not adopt aconfiguration to code-multiplex different users in the same PRB, and thenumber of information bits containable per PRB is larger. Accordingly,even if there is no UL data, an arrangement can be adopted to transmitthe UCI through PUSCH, and thereby to consider this as the high capacityPUCCH format and to transmit the UCI.

The existing PUSCH is transmitted at a specific subframe and a specificPRB, based on PDCCH/EPDCCH from the base station (UL grant prescribed asthe DCI format 0 or DCI format 4) or higher layer signaling. This can bechanged to perform PUSCH transmission, for example, even if there isonly transmission of an HARQ-ACK or CSI.

As regards a PRB or MCS allocated in a PUSCH configuration to transmitthe UCI: this may be specified in advance by higher layer signaling, forexample; or this may be decided based on PDCCH/EPDCCH indicatingdownlink data allocation (DL allocation prescribed as DCI format 1A orDCI format 2D) or information relating to PDSCH on which downlink datais to be transmitted. With this arrangement, there becomes no need totransmit PDCCH to specify a PRB that is used to transmit the highcapacity PUCCH format of the PUSCH type, whereby the overhead of acontrol signal region can be reduced.

Further, conventionally, when having transmitted PUSCH containing ULdata, the user terminal receives PHICH corresponding to PUSCH, anddetermines whether or not to perform retransmission. On the other hand,an HARQ is not applied to PUCCH on which an HARQ-ACK or CSI is to betransmitted. Accordingly, there may be adopted an arrangement such that,when transmitting PUSCH to be used as the high capacity PUCCH format(i.e., it does not contain UL data but contains only UCI), the userterminal does not need to perform reception and detection of PHICHcorresponding to PUSCH. With this arrangement, since the user terminaldoes not need to perform unnecessary PHICH reception, the processingburden of the user terminal can be reduced.

Alternatively, there may be adopted an arrangement such that, whentransmitting PUSCH to be used as the high capacity PUCCH format (i.e.,it does not contain UL data but contains only UCI), the user terminalperforms reception and detection of PHICH corresponding to PUSCH. PUSCHthat does not perform code spreading requires higher reception quality(Signal to Interference plus Noise power Ratio: SINR) as compared withPUCCH. In this way, if PUSCH containing only UCI is treated by givingnotice of a detection result by PHICH and thereby applying an HARQ, itbecomes possible for the base station to reliably receive a controlsignal with high quality.

As described above, according to the first example, it is possible toadequately report a channel state even where the number of componentcarriers settable to the user terminal is expanded to six or more.Further, it is possible to cope with such a demand that particularly theradio base station side is desired to timely acquire the CQIs of theuser terminal.

It should be noted that, in the first example, the period and timing forP-CQI reporting are set to each CC, but the period and timing for P-CQIreporting may be set to each CC group including a plurality of CCs,which is set in advance. For example, in the CCs illustrated in FIG. 3,the CCs #1 to #8, the CCs #9 to #16, the CCs #17 to #24, and the CCs #25to #32 may be sorted into respective CC groups so that the period andtiming can be set to each of the CC groups.

Second Example

In the second example, similarly to the first example, when P-CQIreporting is performed, the high capacity PUCCH format described aboveis used. However, with respect to each CC, an uplink CC (cell), such asa CC to be used for P-CQI reporting, can be set (configured), inaddition to the period and timing for P-CQI reporting.

In the example illustrated in FIG. 4, as regards CCs #1 to #8, inaddition to a period of 20 ms together with timing for performingtransmission at the initial subframe on the uplink illustrated in FIG. 4(the first subframe from the left), there is set use of the CC #1 on theuplink. As regards CCs #9 to #16, in addition to a period of 20 mstogether with timing for performing transmission at the second subframeon the uplink illustrated in FIG. 4 (the second subframe from the left),there is set use of the CC #1 on the uplink. As regards CCs #17 to #24,in addition to a period of 10 ms together with timing for performingtransmission at the first subframe on the uplink illustrated in FIG. 4(the first subframe from the left), there is set use of the CC #2 on theuplink. As regards CCs #25 to #32, in addition to a period of 10 mstogether with timing for performing transmission at the second subframeon the uplink illustrated in FIG. 4 (the second subframe from the left),there is set use of the CC #2 on the uplink.

FIG. 4 illustrates a case where the number of CCs set on the uplink istwo, but this is not limiting. Further, one of a plurality of CCs sethere may be the PCell.

As a result, as illustrated in FIG. 4, in the CC #1 on the uplink, thefirst subframe is used to transmit a plurality of P-CQIs correspondingto the CCs #1 to #8, and the second subframe is used to transmit aplurality of P-CQIs corresponding to the CCs #9 to #16. Further, sincethe CCs #1 to #8 and the CCs #9 to #16 are set with a period of 20 ms,in the CC #1 on the uplink, the 21st subframe is used to transmit thelatest plurality of P-CQIs corresponding to the CCs #1 to #8, and the22nd subframe is used to transmit the latest plurality of P-CQIscorresponding to the CCs #9 to #16.

Further, in the CC #2 on the uplink, the first subframe is used totransmit a plurality of P-CQIs corresponding to the CCs #17 to #24, andthe second subframe is used to transmit a plurality of P-CQIscorresponding to the CCs #25 to #32. Further, since the CCs #17 to #24and the CCs #25 to #32 are set with a period of 10 ms, in the CC #2 onthe uplink, each of the 11th, 21st, and 31st subframes is used totransmit the latest plurality of P-CQIs corresponding to the CCs #17 to#24, and each of the 12th, 22nd, and 32nd subframes is used to transmitthe latest plurality of P-CQIs corresponding to the CCs #25 to #32.

For the control according to the second example, the high capacity PUCCHdescribed above is set in the user terminal. Further, the period andtiming for P-CQI reporting for each of the CCs, and a CC in the uplink,are set from a radio base station by use of RRC or the like. The userterminal transmits P-CQIs of at most eight CCs, at the same subframe, byuse of the high capacity PUCCH format, in accordance with the aboveperiod, timing, and uplink CC. Here, the user terminal in the secondexample is preferably formed of a user terminal that can perform UL CA.The user terminal to which the second example is applied is supposed tohave reported the following terminal abilities to the base station inadvance: It can perform UL CA at a specific frequency by itself, and, atthis time, it can perform P-CQI feedback described in the secondexample.

According to the second example configured as described above, it ispossible to adequately report a channel state even where the number ofcomponent carriers settable to the user terminal is expanded to six ormore. Further, it is possible to cope with such a demand thatparticularly the radio base station side is desired to timely acquirethe CQIs of the user terminal.

In addition, since P-CQI reporting is performed by use of a plurality ofCCs on the uplink, it is possible to avoid performing P-CQI reportingintensively by a specific CC (for example, the CC #1 of the PCell).Further, in the example illustrated in FIG. 4, P-CQIs of at most 16 CCscan be transmitted at the same time by one TTI, and so it is possible toremarkably improve the P-CQI transmission amount per unit transmissiontime. Further, since the P-CQI transmission amount per unit transmissiontime is improved, it is possible to shorten the time necessary for P-CQIreporting in the user terminal. Further, if the capacity of the highcapacity PUCCH format (for example, where the P-CQI information amountcorresponding to one CC is assumed as a unit, the capacity is defined bythe number of units) and/or the number of CCs set in the uplink aresuitably changed, it is possible to perform P-CQI reporting flexibly inaccordance with the P-CQI acquisition request.

Third Example

In the third example, similarly to the second example, P-CQI reportingcan be performed by a plurality of CCs on the uplink, but control isconducted such that P-CQI reporting is performed by the CC #1 of thePCell, as far as possible. However, if the P-CQI reporting amount to betreated by the same subframe exceeds a predetermined amount, P-CQIreporting is performed by a plurality of CCs as in the second example.Accordingly, with respect to each CC, an arrangement can be adopted toset (configure) the period and timing for P-CQI reporting, withoutsetting (configuring) a CC in the uplink.

In the example illustrated in FIG. 5, as regards CCs #1 to #8, there isset a period of 20 ms together with timing for performing transmissionat the initial subframe on the uplink illustrated in FIG. 5 (the firstsubframe from the left). As regards CCs #9 to #16, there is set a periodof 20 ms together with timing for performing transmission at the secondsubframe on the uplink illustrated in FIG. 5 (the second subframe fromthe left). As regards CCs #17 to #24, there is set a period of 10 mstogether with timing for performing transmission at the first subframeon the uplink illustrated in FIG. 5 (the first subframe from the left).As regards CCs #25 to #32, there is set a period of 10 ms together withtiming for performing transmission at the second subframe on the uplinkillustrated in FIG. 5 (the second subframe from the left).

In the user terminal, when P-CQIs of CCs set with the same timing are tobe transmitted, it is determined whether the P-CQI transmission amount(or the number of CCs to be transmitted) exceeds a predetermined value.If the amount exceeds the predetermined value, the P-CQIs are dividedlyallocated to the CC #1 of the PCell and the CC #2 of the SCell, and arethereby transmitted. For example, when a plurality of P-CQIscorresponding to the CCs #1 to #8 and the CCs #17 to #24 set with thefirst subframe for timing are to be transmitted, it is determinedwhether this amount exceeds the transmission amount of P-CQIs of eightCCs, which can be transmitted by use of the high capacity PUCCH format.Since the number of CCs set with the first subframe for timing is 16, itis determined that this amount exceeds the transmission amount of P-CQIsof eight CCs, and so the P-CQIs to be transmitted are dividedlyallocated to the CC #1 of the PCell and the CC #2 of the SCell. As aresult, as illustrated in FIG. 5, in the first subframe, P-CQIscorresponding to the CCs #1 to #8 are allocated to the CC #1, and P-CQIscorresponding to the CCs #17 to #24 are allocated to the CC #2.

Also in the second subframe, processing is performed similarly to thefirst subframe. As a result, as illustrated in FIG. 5, in the secondsubframe, P-CQIs corresponding to the CCs #9 to #16 are allocated to theCC #1, and P-CQIs corresponding to the CCs #25 to #32 are allocated tothe CC #2. Similar processing is performed also at each of the 21stsubframe and the 22nd subframe.

On the other hand, also in the 11th subframe, when a plurality of P-CQIscorresponding to the CCs #17 to #24 set with the 11th subframe fortiming are to be transmitted, it is determined whether this amountexceeds the transmission amount of P-CQIs of eight CCs, which can betransmitted by use of the high capacity PUCCH format. Here, since thenumber of CCs is eight, it is determined that this amount does notexceed the transmission amount of P-CQIs of eight CCs, and so the P-CQIsto be transmitted are allocated to the CC #1 of the PCell. As a result,as illustrated in FIG. 5, at the 11th subframe, P-CQIs corresponding tothe CCs #17 to #24 are allocated to the CC #1, and are therebytransmitted. Similar processing is performed also at each of the 12thsubframe, the 31st subframe, and the 32nd subframe.

As a result of the above, as illustrated in FIG. 5, in the CC #1 on theuplink, each of the first subframe and the 21st subframe is used totransmit the latest plurality of P-CQIs corresponding to the CCs #1 to#8, and each of the second subframe and the 22nd subframe is used totransmit the latest plurality of P-CQIs corresponding to the CCs #9 to#16. Further, each of the 11th subframe and the 31st subframe is used totransmit the latest plurality of P-CQIs corresponding to the CCs #17 to#24, and each of the 12th subframe and the 32nd subframe is used totransmit the latest plurality of P-CQIs corresponding to the CCs #25 to#32.

On the other hand, in the CC #2 on the uplink, each of the firstsubframe and the 21st subframe is used to transmit the latest pluralityof P-CQIs corresponding to the CCs #17 to #24, and each of the secondsubframe and the 22nd subframe is used to transmit the latest pluralityof P-CQIs corresponding to the CCs #25 to #32

For the control according to the third example, the high capacity PUCCHdescribed above is set in the user terminal. Further, the period andtiming for P-CQI reporting for each of the CCs are set from a radio basestation by use of RRC or the like. The user terminal performs thedetermination processing described above (determination as to whether toexceed the transmission amount of P-CQIs of eight CCs, which can betransmitted by use of the high capacity PUCCH format) in accordance withthe above period and timing. If the transmission amount is exceeded, itensures resources dividedly by the CC #1 of the PCell and the CC #2 ofthe SCell, and thereby transmits P-CQIs. Here, the user terminal in thethird example is preferably formed of a user terminal that can performUL CA. The user terminal to which the third example is applied issupposed to have reported the following terminal abilities to the basestation in advance: It can perform UL CA at a specific frequency byitself, and, at this time, it can perform P-CQI feedback described inthe second example.

According to the third example configured as described above, it ispossible to adequately report a channel state even where the number ofcomponent carriers settable to the user terminal is expanded to six ormore. Further, it is possible to cope with such a demand thatparticularly the radio base station side is desired to timely acquirethe CQIs of the user terminal.

In addition, since the coverage of the PCell is usually better in theuplink, and this single CC (uplink cell) is used as far as possible totransmit P-CQIs, it is possible to suppress the battery consumption inthe user terminal. Further, even if all the P-CQIs cannot be transmittedby the CC #1 of the PCell, it is possible to reduce P-CQIs to be stopped(or dropped) in transmission, and thereby to improve the channelfollow-up performance. With respect to each CC, if an arrangement isadopted to set the period and timing for P-CQI reporting, withoutsetting a CC in the uplink, it is possible to reduce the overhead ofhigher layer signaling by an amount corresponding to the setting of aCC, as compared with the second example.

Modification of Third Example

The third example described above determines as to whether to exceed thetransmission amount of P-CQIs of eight CCs, which can be transmitted byuse of the high capacity PUCCH format. If the transmission amount isexceeded, it ensures resources dividedly by the CC #1 of the PCell andthe CC #2 of the SCell, and thereby transmits P-CQIs. However, someconditions may be added to execute such control.

For example, when the P-CQIs are dividedly allocated to the CC #1 of thePCell and the CC #2 of the SCell, the P-CQI of the PCell may be alwaysallocated to the PCell. In general, since the CQI of the PCell isimportant to ensure the connection between the radio base station andthe user terminal, if this is allocated to the PCell, the CQI of thePCell can be reliably received by the radio base station.

Further, in addition to this additional condition, allocation to the CC#1 of the PCell may be made in the ascending order of the cell index. Ingeneral, there are a lot of cases where information transmitted andreceived by a cell with a lower cell index is more important.Accordingly, the above arrangement enables the CQIs of CCs that receivemore important information to be transmitted by the PCell having abetter coverage.

Further, if the total amount of P-CQIs to be transmitted at one subframeexceeds the sum of the capacity of the CC #1 of the PCell and thecapacity of the CC #2 of the SCell, transmission of surplus ones of theP-CQIs may be stopped in accordance with a predetermined condition. Forexample, in accordance with the priority determined in advance,transmission of P-CQIs may be stopped from one concerning informationwith lower priority. As a method of determining the priority, it may bedetermined to give higher priority to a lower cell index in order. Ingeneral, there are a lot of cases where information transmitted andreceived by a cell with a lower cell index is more important.Accordingly, the above arrangement enables the CQIs of CCs that receivemore important information to be transmitted by the PCell having abetter coverage.

Fourth Example

In the fourth example, when transmission of a P-CQI of a specific CC isperformed, the P-CQI of a specific CC is transmitted by use of PUCCHformat 2, 2 a, or 2 b (an existing transmission format). In the fourthexample, the PUCCH format to be used is changed between transmission ofthe P-CQI of a specific CC and transmission of P-CQIs of the other CCs.Information relating to the specific CC can be set (configured) in theuser terminal by use of higher layer signaling, such as RRC.

The fourth example can be applied to any one of the first to thirdexamples described above. Here, with reference to FIG. 6, an explanationwill be given of an example where a method of transmitting only a P-CQIof a specific CC by use of an existing PUCCH format is applied to theabove third example.

FIG. 6 illustrates a case where the specific CC is the CC #1. Further,as regards the CC #1 serving as the specific CC, there is set a periodof 20 ms together with timing for performing transmission at the thirdsubframe on the uplink illustrated in FIG. 6 (the third subframe fromthe left). Accordingly, the user terminal uses the third subframe of theCC #1 to transmit a P-CQI of the CC #1 by use of PUCCH format 2.Similarly, it uses the 23rd subframe to transmit a P-CQI of the CC #1 byuse of PUCCH format 2.

Other than this, there is a difference from the above third example,such that, in the CC #1 of the uplink, each of the first subframe andthe 21st subframe are used to transmit the latest plurality of P-CQIscorresponding to the CC #2 to #8.

For the control according to the fourth example, the high capacity PUCCHformat and an existing PUCCH format are set in the user terminal.Further, the specific CC and the period and timing for P-CQI reportingfor each of the CCs are set from a radio base station by use of RRC orthe like. For the specific CC, the user terminal transmits a P-CQIcorresponding thereto by use of the existing PUCCH format. Further, theuser terminal performs the determination processing described above(determination as to whether to exceed the transmission amount of P-CQIsof eight CCs, which can be transmitted by use of the high capacity PUCCHformat) in accordance with the above period and timing. If thetransmission amount is exceeded, it ensures resources dividedly by theCC #1 of the PCell and the CC #2 of the SCell, and thereby transmitsP-CQIs. Here, the user terminal in the fourth example is preferablyformed of a user terminal that can perform UL CA.

According to the fourth example configured as described above, it ispossible to adequately report a channel state even where the number ofcomponent carriers settable to the user terminal is expanded to six ormore. Further, it is possible to cope with such a demand thatparticularly the radio base station side is desired to timely acquirethe CQIs of the user terminal.

Further, a CC important to ensure the connection between the userterminal and the radio base station is treated as a specific CC and isset at a subframe different from a subframe for transmitting P-CQIs ofthe other CCs. Consequently, it is possible to report only the P-CQI ofthe specific CC, at one subframe, by use of the existing PUCCH, andthereby to improve the certainty of the reception in the radio basestation.

Fifth Example

In the fifth example, if the number of CCs is controlled (or set) to befive or less by CC removal, De-activation, or the like (i.e., if thenumber of CCs becomes equal to or less than that of CA prescribed byRel. 12), P-CQIs are transmitted by use of PUCCH format 2, 2 a, or 2 bfor the existing systems (an existing transmission format). Further, iftimings of a plurality of CCs overlap with each other, only the P-CQI ofa lower cell index CC is kept, and transmission of the P-CQIs of theother CCs is stopped. The fifth example can be applied to any one of thefirst to fourth examples described above.

Next, with reference to FIG. 7, a concrete example will be explained. InFIG. 7, there is assumed a case where, in the above third example, CCsare controlled by use of so-called CC removal for RRC, such that thenumber of CCs is four (CC #1, CC #9, CC #17, and CC #25). Alternatively,there is assumed a case where CCs are controlled by use of so-called CCDe-activation, such that the number of CCs to be activated by the MACcontrol signal (MAC Control Element) is four (CC #1, CC #9, CC #17, andCC #25).

For the control according to the fifth example, the user terminaltransmits P-CQI reporting by use of PUCCH format 2 for the existingsystems. Further, if P-CQIs are set in different uplink CCs but at thesame TTI, the user terminal keeps only the P-CQI of a lower cell indexCC, and stops transmission of the P-CQIs of the other CCs.

For example, at the initial TTI illustrated in FIG. 7 (the leftmostTTI), a P-CQI of the CC #1 and a P-CQI of the CC #17 overlap with eachother. Accordingly, the user terminal compares their cell indexes, andthen transmits the P-CQI of the CC #1 with the lower cell index by useof PUCCH format 2, and stops (or drops) transmission of the P-CQI of theCC #17 with the higher cell index. Similar processing is performed alsoat the 21st TTI.

Further, at the second TTI, a P-CQI of the CC #9 and a P-CQI of the CC#25 overlap with each other. Accordingly, the user terminal comparestheir cell indexes, and then transmits the P-CQI of the CC #9 with thelower cell index by use of PUCCH format 2, and stops (or drops)transmission of the P-CQI of the CC #25 with the higher cell index.Similar processing is performed also at the 22nd TTI.

On the other hand, at each of the 11th TTI and the 31st TTI, there is nooverlap of P-CQIs, and so a P-CQI of the CC #17 is transmitted by use ofPUCCH format 2. Similarly, at each of the 12th TTI and the 32nd TTI,there is no overlap of P-CQIs, and so a P-CQI of the CC #25 istransmitted by use of PUCCH format 2.

Further, if the number of CCs activated exceeds five (i.e., if CCs areactivated in a number not prescribed by Rel. 12) because of CC additionor CC activation, P-CQI reporting using the high capacity PUCCH formatis applied.

According to the fifth example configured as described above, it ispossible to adequately report a channel state even where the number ofcomponent carriers settable to the user terminal is expanded to six ormore. Further, where the number of component carriers is set to five orless, an existing communication technique is applied, and so it ispossible to obtain backward compatibility. Further, where the number ofcomponent carriers settable to the user terminal is expanded to six ormore, it is possible to cope with such a demand that the radio basestation is desired to timely acquire the CQIs of the user terminal.

(Modifications)

In the first to fifth examples described above, some modifications maybe considered.

For example, in the high capacity PUCCH format, there may be consideredprocessing for a case where a P-CQI and a scheduling request (SR)overlap with each other. Specifically, if a P-CQI and a schedulingrequest overlap with each other, the scheduling request is prioritizedover the P-CQI, and is transmitted on PUCCH of the PCell. In this case,in the user terminal, control is performed to regard the schedulingrequest as information higher in priority than the P-CQI. Other thanthis, if there is a scheduling request, it is transmitted by use ofPUCCH format 2, 2 a, or 2 b (an existing transmission format). In thiscase, since P-CQIs of a plurality of CCs cannot be transmitted at thesame subframe, only transmission of a P-CQI of one CC is performed,based on priority using cell indexes or the like, and transmission ofP-CQIs corresponding to the other CCs is stopped.

Other than the above, there may be considered processing for a casewhere a P-CQI and a SRS (Sounding Reference Signal) overlap with eachother on the same CC. In this case, transmission of the SRS may bestopped. Further, in the case of a Periodic SRS (P-SRS) in which theperiod and/or resource of the SRS are set by use of higher layersignaling, control may be performed to prioritize the P-CQI; and, in thecase of an Aperiodic SRS (A-SRS) which is triggered by UL grant, controlmay be performed to prioritize the A-SRS and to stop transmission of theP-CQI.

Other than the above, there may be considered processing for a casewhere simultaneous transmission of P-CQIs is performed by a plurality ofCCs (transmission at the same TTI) and the user terminal has fallen intoa Power-limited state. In this case, one of the following arrangementsmay be adopted: 1) Power (transmission) for a P-CQI by the PCell isprioritized, and P-CQIs to be transmitted by the SCell are stopped (ordropped) or are subjected to Power-scale. 2) In order to put priority ona scheduling request, power (transmission) for a P-CQI multiplexed bythe scheduling request is prioritized, and the other P-CQIs are stoppedor are subjected to Power-scale. 3) Based on comparison in the number ofCCs multiplexed, power (transmission) for P-CQIs multiplexed in thelargest number of CCs is prioritized, and the other P-CQIs are stoppedor are subjected to Power-scale.

(Configuration of Radio Communication System)

Next, an explanation will be given of the configuration of a radiocommunication system according to an embodiment of the presentinvention. In this radio communication system, any one or combination ofthe first to fifth examples (including the modifications) is applied.

FIG. 8 is a schematic configuration diagram illustrating an example ofthe radio communication system according to this embodiment of thepresent invention. As illustrated in FIG. 8, the radio communicationsystem 1 includes a plurality of radio base stations 10 (11 and 12 (12 ato 12 c)), and a plurality of user terminals 20, which are presentwithin cells formed by the respective radio base stations 10 and areconfigured to communication with the respective radio base stations 10.The radio base stations 10 are respectively connected to a higherstation apparatus 30, and are connected to a core network 40 via thehigher station apparatus 30.

In FIG. 8, the radio base station 11 is formed of, e.g., a macro basestation having a relatively wide coverage, and provides a macro cell C1.Each of the radio base stations 12 (12 a to 12 c) is formed of a smallbase station having a localized coverage, and provides a small cell C2.Here, the number of radio base stations 11 and 12 is not limited to thatillustrated in FIG. 8.

The macro cell C1 and the small cells C2 may use the same frequencyband, or may use different frequency bands. Further, the radio basestations 11 and 12 are connected to each other via an inter-base stationinterface (for example, an optical fiber or X2 interface).

Here, the macro base station 11 may be referred to as “radio basestation”, “eNodeB(eNB)”, or “transmission point”. The small basestations 12 may be referred to as “pico base station”, “femto basestation”, “Home eNodeB(HeNB)”, “transmission point”, or “RRH” (RemoteRadio Head).

Each of the user terminals 20 is a terminal corresponding to variouscommunication schemes, such as LTE and LTE-A, and may encompass not onlya mobile communication terminal but also a stationary communicationterminal. Each user terminal 20 can perform communication with the otheruser terminals 20 via the radio base stations 10.

For example, the higher station apparatus 30 encompasses an accessgateway device, radio network controller (RNC), mobility managemententity (MME), and the like, but this is not limiting.

In the radio communication system 1, as radio access schemes, OFDMA(orthogonal frequency division multiple connection) is applied to thedownlink, and SC-FDMA (single carrier-frequency division multipleconnection) is applied to the uplink. OFDMA is a multicarriertransmission scheme for dividing a frequency band into a plurality ofnarrower frequency bands (subcarriers) and performs communication bymapping data onto the respective subcarriers. SC-FDMA is a singlecarrier transmission scheme for dividing a system bandwidth into bandsformed of one or serial resource blocks for each terminal, and aplurality of terminals respectively use bands different from each otherto reduce interference among the terminals. Here, the radio accessschemes of the uplink and the downlink are not limited to thiscombination.

In the radio communication system 1, as the downlink channels, there areused a downlink shared channel (PDSCH: Physical Downlink Shared Channel)shared by the respective user terminals 20, a broadcast channel (PBCH:Physical Broadcast Channel), downlink L1/L2 control channels, and thelike. On PDSCH, user data, higher layer control information, and/orpredetermined SIB (System Information Block) are transmitted. Further,on PBCH, a synchronous signal, MIB (Master Information Block), and/orthe like are transmitted.

The downlink L1/L2 control channels include PDCCH (Physical DownlinkControl Channel), EPDCCH (Enhanced Physical Downlink Control Channel),PCFICH (Physical Control Format Indicator Channel), PHICH (PhysicalHybrid-ARQ Indicator Channel), and the like. On PDCCH, Downlink ControlInformation (DCI) including scheduling information relating to PDSCH andPUSCH, and the like, are transmitted. On PCFICH, an OFDM symbol numberused for PDCCH is transmitted. On PHICH, an HARQ deliveryacknowledgement signal (ACK/NACK) with respect to PUSCH is transmitted.EPDCCH may be treated together with PDSCH (downlink shared data channel)by frequency division multiple, and used to transmit the DCI or the likesimilarly to PDCCH.

In the radio communication system 1, as the uplink channels, there areused an uplink shared channel (PUSCH: Physical Uplink Shared Channel)shared by the respective user terminals 20, an uplink control channel(PUCCH: Physical Uplink Control Channel), a random access channel(PRACH: Physical Random Access Channel), and the like. On PUSCH, userdata and/or higher layer control information are transmitted. Further,on PUCCH, downlink radio quality information (CQI: Channel QualityIndicator), delivery acknowledgement signal, and/or the like aretransmitted. On PRACH, a random access preamble (RA preamble) forestablishing connection to a cell is transmitted. Further, as uplinkreference signals, there are transmitted a reference signal formeasuring the channel quality (SRS: Sounding Reference Signal), and ademodulation reference signal (DM-RS: Demodulation Reference Signal) fordemodulating PUCCH and/or PUSCH.

FIG. 9 is a diagram illustrating an example of the entire configurationof each of the radio base stations 10 according to this embodiment. Eachradio base station 10 (encompassing the radio base stations 11 and 12)includes a plurality of transmission/reception antennas 101 for MIMOtransmission, amplifying sections 102, transmission/reception sections103, a baseband signal processing section 104, a call processing section105, and a transmission path interface 106. Here, eachtransmission/reception section 103 is formed of a transmission sectionand a reception section.

User data to be transmitted from each radio base station 10 to a userterminal 20 by the downlink is input from the higher station apparatus30 through the transmission path interface 106 to the baseband signalprocessing section 104.

In the baseband signal processing section 104, the user data issubjected to transmission processing, such as: PDCP (Packet DataConvergence Protocol) layer processing; division and join of the userdata; RLC layer transmission processing, such as RLC (Radio LinkControl) retransmission control; MAC (Medium Access Control)retransmission control (for example, HARQ (Hybrid Automatic RepeatreQuest) transmission processing); scheduling; transmission formatselection; channel coding; Inverse Fast Fourier Transform (IFFT)processing; pre-coding processing; and/or the like. Then, the user datais transferred to each transmission/reception section 103. Further, alsoa downlink control signal is subjected to transmission processing, suchas channel coding and/or inverse fast Fourier transform, and istransferred to each transmission/reception section 103.

Each transmission/reception section 103 converts a downlink signal,which has been output from the baseband signal processing section 104 ina pre-coded state for each antenna, into a signal of a radio frequencyband, and transmits it. The radio frequency signal converted infrequency by each transmission/reception section 103 is amplified by thecorresponding amplifying section 102 and transmitted from thecorresponding transmission/reception antenna 101. Eachtransmission/reception section 103 may be formed of atransmitter/receiver, transmission/reception circuit, ortransmission/reception device, utilized in the technical field of thepresent invention.

On the other hand, as regards uplink signals, a radio frequency signalreceived by each transmission/reception antenna 101 is amplified by thecorresponding amplifying section 102. Each transmission/receptionsection 103 receives the uplink signal amplified by the correspondingamplifying section 102. Each transmission/reception section 103 convertsin frequency the reception signal into a baseband signal, and outputs itto the baseband signal processing section 104.

In the baseband signal processing section 104, user data contained inthe input uplink signal is subjected to: Fast Fourier Transform (FFT)processing; Inverse Discrete Fourier Transform (IDFT) processing; errorcorrection decoding; MAC retransmission control reception processing;and/or RLC layer and PDCP layer reception processing. Then, the userdata is transferred via the transmission path interface 106 to thehigher station apparatus 30. The call processing section 105 performs:call processing, such as setting or releasing of a communicationchannel; state management of the radio base stations 10; and/or radioresource management.

The transmission path interface 106 transmits and receives a signal withrespect to the higher station apparatus 30 via a predeterminedinterface. Further, the transmission path interface 106 may transmit andreceive (backhaul signaling) a signal with respect to an adjacent radiobase station via an inter-base station interface (for example, anoptical fiber or X2 interface).

FIG. 10 is a principal function configuration diagram of the basebandsignal processing section 104 included in each of the radio basestations 10 according to this embodiment. Here, in FIG. 10, thefunctional block of a characterizing part according to this embodimentis mainly shown, but each radio base station 10 is supposed to includeother functional blocks necessary for radio communication.

As illustrated in FIG. 10, each radio base station 10 is configured byincluding at least a control section (scheduler) 301, a transmissionsignal generating section 302, and a reception processing section 303.

The control section (scheduler) 301 controls scheduling of a downlinkdata signal to be transmitted on PDSCH and a downlink control signal tobe transmitted on PDCCH and/or expanded PDCCH (EPDCCH). Further, thecontrol section 301 performs control of scheduling of systeminformation, synchronization signal, downlink control signals, such asCRS, CSI-RS, and the like. Further, the control section 301 performscontrol of scheduling of an uplink reference signal, an uplink datasignal to be transmitted on PUSCH, and an uplink control signal to betransmitted on PUCCH and/or PUSCH. Here, the control section 301 may beformed of a controller, control circuit, or control device, utilized inthe technical field of the present invention.

Further, the control section 301 can control the transmission signalgenerating section 302, to control CCs treated as measurement targets ina user terminal 20 connected in this radio base station 10.Specifically, the control section 301 notifies the transmission signalgenerating section 302 of CC information contained in a TAG, andcontrols it to generate a signal containing this CC information (forexample, higher layer signaling), (the first example). Further, thecontrol section 301 notifies the transmission signal generating section302 of a measurement gap configuration set in each TAG, and controls itto generate a signal containing this measurement gap configuration (forexample, higher layer signaling), (the second example).

Based on an instruction from the control section 301, the transmissionsignal generating section 302 generates a DL signal (a downlink controlsignal, downlink data signal, downlink reference signal, or the like).For example, based on CC information contained in a timing advance group(TAG) sent from the control section 301, the transmission signalgenerating section 302 generates a signal containing this CC information(the first or second example). In this case, the transmission signalgenerating section 302 may generate a signal containing a CC list in theTAG (the first or second example). Further, based on a measurement gapconfiguration set in each TAG sent from the control section 301, thetransmission signal generating section 302 generates a signal containingthis measurement gap configuration (the second example). The informationof these kinds is sent from each transmission/reception section 103 to auser terminal 20 by use of higher layer signaling (for example, RRCsignaling or a broadcast signal) or a downlink control signal. Here, thetransmission signal generating section 302 may be formed of a signalgenerator or signal generating circuit, utilized in the technical fieldof the present invention.

The reception processing section 303 performs reception processing (forexample, demapping, demodulation, decoding, and/or the like) to a ULsignal (such as an uplink control signal, uplink data signal, or uplinkreference signal) transmitted from a user terminal 20. For example, thereception processing section 303 performs reception processing (such asmeasurement of reception power (RSRP) or channel state) to a measurementresult transmitted from a user terminal 20. More specifically, thereception processing section 303 performs reception processing to ameasurement result for each TAG transmitted from a user terminal 20 (thefirst example). Further, the reception processing section 303 performsreception processing to a measurement result for each CC transmittedfrom a user terminal 20 (the second example). Then, the receptionprocessing section 303 outputs a measurement result subjected toreception processing to the control section 301. Here, the receptionprocessing section 303 may be formed of a signal processor or signalprocessing circuit, utilized in the technical field of the presentinvention.

FIG. 11 is a diagram illustrating an example of the entire configurationof each of the user terminals 20 according to the embodiment of thepresent invention. As illustrated in FIG. 11, each user terminal 20includes a plurality of transmission/reception antennas 201 for MIMOtransmission, amplifying sections 202, transmission/reception sections203, a baseband signal processing section 204, and an applicationsection 205. Here, each transmission/reception section 203 may be formedof a transmission section and a reception section.

Radio frequency signals respectively received by the plurality oftransmission/reception antennas 201 are amplified by the amplifyingsections 202. Each transmission/reception section 203 receives adownlink signal amplified by the corresponding amplifying section 202.Each transmission/reception section 203 converts in frequency thereception signal into a baseband signal, and outputs it to the basebandsignal processing section 204. Each transmission/reception section 203may be formed of a transmitter/receiver, transmission/reception circuit,or transmission/reception device, utilized in the technical field of thepresent invention.

The baseband signal processing section 204 performs receptionprocessing, such as FFT processing, error correction decoding, and/orretransmission control to the input baseband signal. User data on thedownlink is transferred to the application section 205. The applicationsection 205 performs processing and the like concerning layers higherthan the physical layer and MAC layer. Further, of the downlink data,broadcast information is also transferred to the application section205.

On the other hand, uplink user data is input from the applicationsection 205 to the baseband signal processing section 204. In thebaseband signal processing section 204, the user data is subjected to:retransmission control transmission processing (for example, HARQtransmission processing); channel coding; pre-coding; Discrete FourierTransform (DFT) processing; IFFT processing; and/or the like. Then, theuser data is transferred to each transmission/reception section 203.Each transmission/reception section 203 converts a baseband signal,which has been output from the baseband signal processing section 204,into a signal of a radio frequency band, and transmits it. The radiofrequency signal converted in frequency by each thetransmission/reception sections 203 is amplified by the correspondingamplifying section 202 and transmitted from the correspondingtransmission/reception antenna 201.

Each transmission/reception section 203 can transmit and receive asignal with respect to a radio base station that sets a TAG composed ofone or more cells. Further, each transmission/reception section 203 cantransmit and receive signals with respect to a plurality of radio basestations that respectively sets cell groups (CG) composed of one or morecells.

FIG. 12 is a principal function configuration diagram of the basebandsignal processing section 204 included in each of the user terminals 20.Here, in FIG. 12, the functional block of a characterizing partaccording to this embodiment is mainly shown, but each user terminal 20is supposed to include other functional blocks necessary for radiocommunication.

As illustrated in FIG. 12, each user terminal 20 is configured byincluding at least a reception signal processing section 401, ameasuring section 402, a control section 403, and a transmission signalgenerating section 404.

The reception signal processing section 401 performs receptionprocessing (for example, demapping, demodulation, decoding, and/or thelike) to a DL signal (for example, a downlink control signal transmittedfrom a radio base station, downlink data signal transmitted on PDSCH,and/or the like). The reception signal processing section 401 outputsinformation, which has been received from a radio base station 10, tothe control section 403. For example, the reception signal processingsection 401 outputs broadcast information, system information, paginginformation, RRC signaling, and/or DCI to the control section 403.

The reception signal processing section 401 may be formed of a signalprocessor, signal processing circuit, or signal processing device, and ameasuring instrument, measuring circuit, or measuring device, which areexplained based on the common view in the technical field of the presentinvention.

The measuring section 402 measures reception power (RSRP), receptionquality (RSRQ), and/or channel state by use of a reception signal, andoutputs this result to the control section 403. Particularly, in thisembodiment, the above measurement is performed to each of the CCs of CA.

The control section 403 generates P-CQIs, based on measurement resultsobtained by the measuring section 402 and various kinds of information(the period, timing, CCs, and specific CC for P-CQI reporting) sent froma radio base station 10 via the reception signal processing section 401.Further, the control section 403 instructs the transmission signalgenerating section 404 as to how to allocate the P-CQIs to uplinkresources.

According to the first example described above, the high capacity PUCCHis set in the user terminal 20, and the control section 403 instructsthe transmission signal generating section 404 to transmit P-CQIs of atmost eight CCs, at the same subframe (the same TTI), by use of the highcapacity PUCCH format, in accordance with the period and timing.

According to the second example described above, the control section 403instructs the transmission signal generating section 404 to transmitP-CQIs of at most eight CCs, at the same subframe, by use of the highcapacity PUCCH format, in accordance with the period, timing, and CC.

According to the third example described above, determination processingis performed (determination as to whether to exceed the transmissionamount of P-CQIs of eight CCs, which can be transmitted by use of thehigh capacity PUCCH format) in accordance with the period and timing. Ifthe transmission amount is exceeded, the control section 403 instructsthe transmission signal generating section 404 to ensure resourcesdividedly by the CC #1 of the PCell and the CC #2 of the SCell, andthereby transmit P-CQIs.

According to the fourth example described above, as regards only aspecific CC, the control section 403 instructs the transmission signalgenerating section 404 to transmit the P-CQI of the specific CC by useof an existing PUCCH format (for example, PUCCH format 2). Further, asregards the P-CQIs of the other CCs, the determination processing isperformed (determination as to whether to exceed the transmission amountof P-CQIs of eight CCs, which can be transmitted by use of the highcapacity PUCCH format). If the transmission amount is exceeded, thecontrol section 403 instructs the transmission signal generating section404 to ensure resources dividedly by the CC #1 of the PCell and the CC#2 of the SCell, and thereby transmit P-CQIs.

According to the fifth example described above, if the number of CCs isset to be five or less by CC removal, De-activation, or the like, thecontrol section 403 instructs the transmission signal generating section404 to transmit P-CQI reporting by use of PUCCH format 2 for theexisting systems. At this time, even among different CCs, if P-CQIsoverlap with each other at the same TTI, the control section 403instructs the transmission signal generating section 404 to transmitonly the P-CQI of a lower cell index CC, while stopping transmission ofthe P-CQIs of the other CCs.

The control section 403 may be formed of a controller, control circuit,or control device, which is explained based on the common view in thetechnical field of the present invention.

Based on an instruction from the control section 403, the transmissionsignal generating section 404 generates a UL signal, performs mappingprocessing thereto, and outputs it to the transmission/receptionsections 203. Based on an instruction from the control section 403, thetransmission signal generating section 404 generates an uplink controlsignal, such as a delivery acknowledgement signal (HARQ-ACK), channelstate information (CSI), or the like. Further, based on an instructionfrom the control section 403, the transmission signal generating section404 generates an uplink data signal. For example, if UL grant iscontained in a downlink control signal sent from a radio base station10, the transmission signal generating section 404 is instructed by thecontrol section 403 to generate an uplink data signal.

It should be noted that block diagrams used for the description of theabove embodiment show functional unit blocks. Each of these functionalblocks (configuration sections) is realized by an arbitrary combinationof hardware and software. Further, means for realizing each functionalblock is not limited to a specific one. In other words, each functionalblock may be realized by a single device physically integrated, or maybe realized by a plurality of devices in which two or more devicesphysically separated are connected by cable or radio.

For example, some or all of the respective functions of each of theradio base stations 10 and the user terminals 20 may be realized by useof hardware, such as an ASIC (Application Specific Integrated Circuit),PLD (Programmable Logic Device), and/or FPGA (Field Programmable GateArray). Further, each of the radio base stations 10 and the userterminals 20 may be realized by a computer apparatus including aprocessor (CPU), a communication interface for network connection, amemory, and a computer readable storage medium that holds programs.

Here, the processor, the memory, and so forth are connected to eachother by a bus for communicating information. Further, the computerreadable storage medium is a storage medium, such as a flexible disk,magneto-optical disk, ROM, EPROM, CD-ROM, RAM, or hard disk, forexample. Further, the program may be transmitted from a network via anelectric communication line. Further, each of the radio base stations 10and the user terminals 20 may include an input device, such as inputkeys, and/or an output device, such as a display.

A functional configuration of each of the radio base stations 10 and theuser terminals 20 may be realized by the hardware described above, maybe realized by a software module to be executed by a processor, or maybe realized by a combination of both of them. The processor operates anoperating system to control the entirety of the corresponding userterminal. Further, the processor reads a program, software module, ordata from the storage medium into the memory, and performs processing ofvarious kinds in accordance with the read program or the like. Here, theprogram only needs to be a program that causes a computer to perform therespective operations described in the embodiment. For example, thecontrol section 301 of each radio base station 10 may be realized by acontrol program that is stored in the memory and is operated by theprocessor, and the other functional blocks may also be realizedsimilarly.

Although the present invention has been described in detail above, itwill be obvious to those skilled in the art that the present inventionis not limited to the embodiment described in the specification. Forexample, the respective aspects described above may be used each alone,or may be used in combination. The present invention can be implementedas modified and altered aspects without departing from the sprit andscope of the present invention as defined by the scope of the Claims.Accordingly, the description of the specification is for the purpose ofillustrative explanation, and does not have any restrictive meaning tothe present invention.

The present application is based on Japanese Patent Application No.2015-016019 filed on Jan. 29, 2015, which is incorporated by referenceherein in its entirety.

1. A user terminal for communicating with a radio base station by use ofsix or more component carriers, the user terminal comprising: ameasuring section configured to measure reception quality of a downlinkchannel of each of the component carriers; and a transmission sectionconfigured to periodically transmit information relating to thereception quality in accordance with timing specified from the radiobase station, wherein the transmission section transmits informationrelating to reception quality of a plurality of component carriers, at asame subframe, by use of PUSCH or a PUCCH format having a largercapacity as compared with a PUCCH format for existing systems in which anumber of configured component carriers is five or less.
 2. The userterminal according to claim 1, wherein the transmission sectiontransmits information relating to reception quality of a plurality ofcomponent carriers, based on timing associated with each componentcarrier and information relating to a component carrier that is used totransmit information relating to reception quality.
 3. The user terminalaccording to claim 1, wherein, in the case of transmitting informationrelating to reception quality of a plurality of component carriers at asame subframe, when an amount of the information relating receptionquality of a plurality of component carriers is equal to or less than apredetermined value, the transmission section transmits the informationrelating to reception quality of a plurality of component carriers byuse of a specific component carrier, and, when the amount exceeds thepredetermined value, the transmission section divides and transmits theinformation relating to reception quality of a plurality of componentcarriers by use of the specific component carrier and another componentcarrier.
 4. The user terminal according to claim 3, wherein thetransmission section preferentially transmits information that indicatesreception quality of a component carrier with higher priority configuredbased on a cell index among the plurality of component carriers, by useof the specific component carrier.
 5. The user terminal according toclaim 3, wherein the predetermined value is a sum of a capacity of thespecific component carrier and a capacity of the another componentcarrier, and the transmission section stops transmission of informationthat indicates reception quality corresponding to a surplus capacityexceeding the predetermined value, in accordance with predeterminedpriority.
 6. The user terminal according to claim 1, wherein, whentransmitting reception quality of one component carrier, at onesubframe, the transmission section performs transmission by use of PUCCHformat 2, 2 a, or 2 b for existing systems.
 7. The user terminalaccording to claim 6, wherein, when a number becomes five or less forthe plurality of configured component carriers, the transmission sectionperforms transmission of information relating to reception quality ofrespective component carriers individually by use of a PUCCH format 2, 2a, or 2 b.
 8. A radio base station for communicating with a userterminal that utilizes six or more component carriers, the radio basestation comprising: a notifying section configured to notify the userterminal of transmission timing for periodically transmittinginformation relating to reception quality of a downlink channel to bemeasured in the user terminal; and a reception section configured toreceive information relating to reception quality of a plurality ofcomponent carriers, at a same subframe, by use of PUSCH or a PUCCHformat having a larger capacity as compared with a PUCCH format forexisting systems in which a number of configured component carriers isfive or less.
 9. (canceled)
 10. A radio communication method in user tenAnal for communicating with a radio base station by use of six or morecomponent carriers, the radio communication method comprising: measuringreception quality of a downlink channel of each of the componentcarriers; and periodically transmitting information relating to thereception quality in accordance with timing specified from the radiobase station, wherein the transmitting includes transmitting informationrelating to reception quality of a plurality of component carriers, at asame subframe, by use of PUSCH or a PUCCH format having a largercapacity as compared with a PUCCH format for existing systems in which anumber of configured component carriers is five or less.